At the moment, all my parts are stock parts. Though if these issues keep up, perhaps I will have to consider switching to a different hotend...
I tinkered some more with much higher retraction speeds and distances, to the point where cura was turning the boxes orange. But it doesn't seem to be doing anything. I also turned on the 'coasting' setting, where the end of the extrusion path is turned into a travel move and increased the travel speed, but still the strings!
Is it possible there is some issue in the hot end? I can see that the filament is retracting but that doesn't seem to be relieving any pressure. I even timed it so I stopped the print when the filament was retracted and a lot of material oozed out right away. Any thoughts?